PROJECT SUMMARY: Children with NUP98-rearranged acute leukemias demonstrate a poor response to conventional therapy and are associated a high rate of relapsed disease and poor overall outcome. These fusions account for approximately 10% of children with AML, yet our overall understanding of the molecular consequences of fusion oncoprotein expression has been limited in part by a paucity of suitable model systems. Different types of NUP98 fusion partners exist and recent work from our group and others have shown that these different fusions are associated with unique clinical, morphologic and genomic features. For example, children with a NUP98-KDM5A fusion commonly present with an AML with either erythroid or megakaryoblastic features and can have an associated RB1 loss of function mutation. In contrast, NUP98-NSD1, which is the most frequent NUP98 fusion, more commonly is associated with myelomonocytic features and co-occurring FLT3 and/or WT1 mutations. These genomic and clinical findings establish a strong scientific premise to investigate the molecular impact of different NUP98 fusions in hematopoietic cells. We hypothesize that different NUP98 oncoproteins will drive the expression of specific transcriptional networks, in part through unique cooperating mutations, and provide potential vulnerabilities that can be exploited by epigenetic targeted therapies. We will test our hypothesis with the following specific aims using a combination of genetic tools in human and mouse hematopoietic cells; Specific Aim 1: To determine the in vitro molecular impact of different NUP98 fusions in primary hematopoietic cells. Specific Aim 2: To co-model patterns of genomic alterations observed in patients to establish new in vivo models of NUP98-rearranged leukemias. Specific Aim 3: To utilize genome editing and small molecule screens to identify and exploit therapeutic vulnerabilities for NUP98 leukemias. Not only will the proposed studies elucidate the transcriptional and epigenetic impact of NUP98 fusion oncoprotein expression and potentially identify vulnerabilities that can exploited, but we will also establish multiple mouse and human model systems, including PDX, that will faithfully recapitulate the diseases observed in children. This will provide both the other Projects in this consortium grant and greater the scientific field with necessary tools to ultimately develop therapeutic approaches to target NUP98-fusion oncoproteins and most importantly to improve the long-term outcome of children with these leukemias.